1. Field of the Invention
This invention relates to a metal detector wherein a wand is extendable and retractable between a full-sized state and a reduced, compact state. The full-sized state comprises the normal in-use condition. When the wand is retracted, the detector is compact enough to be comfortably carried with or without the use of the hands in the field for extended periods of time, preferably compact enough to fit in a holster attached to the belt of the user.
2. Description of Related Art
Metal detectors are used to locate and ofttimes trace underground or otherwise unseen metal objects, e.g., cables, pipes, land mines, boundary markers, etc. Many different sensor constructions are used to accomplish these purposes, but the designs of the detector bodies can broadly be divided into two categories: (1) a disc type in which a relatively flat sensor disc is attached to the bottom of a long, thin wand and a housing for the controls, display, and detector circuitry is attached to the top of the wand, and (2) a wand type in which the control and display housing is mounted atop a light but relatively bulky wand.
The former are characterized by the flat disc being held close to the ground and substantially parallel thereto, and the detector is carried by a handle located on the control and display housing remote from the disc. Because the weight of the detector is divided between the disc and the housing, which are widely separated from each other by the wand, a large moment of force is created. In order to minimize the fatigue produced thereby, it is common to design the wand to be slightly telescopic, so that the length of the wand may be adjusted to a limited extent in order to fit it to the height of the user, thus reducing the apparent weight of the detector. Representative of this type are the design patents to Doss (U.S. Pat. No. Des. 218,705), Gardiner (U.S. Pat. No. Des. 224,441), Schaefer et al. (U.S. Pat. No. Des. 274,607), Yue (U.S. Pat. No. Des. 377,908), and Adolphs (U.S. Pat. No. Des. 419,458) and the utility patents to Rist et al. (U.S. Pat. No. 3,769,575), Anderson (U.S. Pat. No. 3,823,365), and Wollny (U.S. Pat. No. 5,680,048). See Anderson, column 3, lines 8-12, and Wollny, column 4, lines 44-46, for teachings of adjusting the length of the wand. Rist et al. teaches making the wand in sections for easy disassembly and storage; column 3, lines 34-36. To inventors"" knowledge, none of the disc type detectors teach nor disclose structure which will permit retracting the wand for easy carrying.
Wand-type metal detectors are characterized by a control, display, and circuitry housing being located atop a light wand. A handle is either built into the housing or extends laterally therefrom. The vast majority of the weight of the detector, therefore, is concentrated in the housing, so fatigue-producing moments of force are virtually nonexistent, and the detectors are easy to handle.
Another characteristic of wand-type metal detectors is that there are a plurality of sensors distributed about the detector body in a precise configuration. The orientation of the sensors are usually fixed relative to each other in order for the detector to work most efficiently.
Because of these two factors (concentration of weight in the housing and fixed orientation of the sensors), none of the known wand-type detectors have telescoping wands. The sensors are located differently for different purposes, but the housing/wand combinations are universally designed as integral and rigid. In some instances, the sensors are located both in the wand and the combination handle/circuitry housing atop the wand (Tavernetti et al., U.S. Pat. No. 5,043,666; Peterman et al., U.S. Pat. No. 5,001,430). In others, they are spaced apart in the wand, in the housing, and in wings extending from one or both (Peterman, U.S. Pat. No. 4,520,317). Finally, the most common wand-type detectors are those in which the sensors are spaced apart within the wand alone (Schondstedt, U.S. Pat. No. Des. 255,552; Power, U.S. Pat. No. Des. 459,245; Power et al., U.S. Pat. No. Des. 459,246; Rippingale, U.S. Pat. No. 4,818,944; Balkman, U.S. Pat. No. 5,093,622; Parkinson et al., U.S. Pat. No. 5,430,379; Archambeault et al., U.S. Pat. No. 5,469,155; Reinhardt, U.S. Pat. No. 5,578,926; Eslambolchi et al., U.S. Pat. No. 5,644,237 and U.S. Pat. No. 5,798,644; and Hanlon et al., U.S. Pat. No. 5,828,219).
In one apparent exception to the rigid wand standard, the patent to Peterman et al., U.S. Pat. No. 5,001,430, shows in FIG. 1 a wand which appears to be in two sections having different diameters with a ferrule located at the intersection of the two. The combination resembles the adjusting mechanism for the legs of a photographic tripod, wherein rotation of the ferrule locks or releases the legs for telescopic adjustments. The specification makes no mention of the feature, however, so all assumptions concerning its structure and functions are nothing but guesswork. To complicate matters, the specification speaks only of the wand in the singular as if it consists of only one piece. And, the specification requires the sensors located on opposite sides of the ferrule to be fixed relative to each other, which further suggests the housing and wand are all of one piece construction. The reasonable conclusion drawn by one skilled in the art is that the wand is non-telescopic regardless of the drawing. Whatever xe2x80x9cteachingxe2x80x9d the inventors intended by the drawing is lost in the confusion.
All patents mentioned herein are of record.
It is common, when searching for isolated, passive objects buried underground, as with a magnetic detector, to be forced to carry a metal detector for long periods of time over a variety of landscapes, some so rugged that both hands are needed to get through them. To date, the user has been required to constantly carry the detector in one or both hands. Even detectors which are comfortable at first become uncomfortable to carry in time. A detector which is sufficiently compact in size such that it can be transported comfortably for extended periods of time with one hand would be a distinct improvement. One which can be comfortably transported without the use of either hand would meet the needs of those in the art. The disclosed invention satisfies these needs.
The present invention overcomes the difficulties described above by providing a metal detector with a retractable/extendable wand, such that when retracted, the detector is sufficiently compact as to be carried comfortably in the field with and preferably without the use of hands.
It is an object of the invention to provide a metal detector which can be reduced in size sufficiently to fit within a holster provided therefor.
It is a further object of the invention to provide a metal detector which can be carried for long periods of time without tiring.
It is a further object of the invention to provide a metal detector which can be retracted for easy carrying and for facilitating the storage thereof.